1. Field of the Invention
This invention relates to a door latch for securing the free end of a hinged door. More particularly, the present invention concerns a sliding latch mechanism for freely engaging a door to maintain the door in a sealed position.
2. Prior Art
A typical rooftop type air conditioning unit includes a refrigeration circuit having a compressor, condenser and evaporator located in a cabinet mounted on the roof of or adjacent to an enclosure to be conditioned. Air is circulated between the enclosure to be conditioned and the rooftop unit. A portion of the rooftop unit is utilized to define a flow path for the air being circulated, said air passing in heat exchange relation with a portion of the refrigeration circuit within the unit.
The typical rooftop unit is divided into an indoor section and an outdoor section. The outdoor section may include the condenser and compressors of the refrigeration circuit. Outdoor ambient air is circulated over the condenser to effect heat transfer from the refrigerant flowing through the condenser to the air such that the refrigerant is cooled and changes state from a gas to a liquid. The refrigerant then travels to an evaporator located within the indoor section of the unit. Within the evaporator, the refrigerant changes state from a liquid to a gas absorbing its heat of vaporization from air flowing through the indoor section. This indoor air is typically circulated back to the enclosure to be conditioned to provide a supply of cooled air. A fan may be mounted within the indoor section for circulating air back to the enclosure. The refrigerant then flows from the evaporator back to the compressor where it is increased in temperature and pressure and then circulated to the condenser to complete the cycle.
In order to properly service an air conditioning unit, access must be had to the interior thereof. Access is typically made available through a hinged or other type door opening to allow the serviceman to repair or inspect the evaporator, indoor fan or other components in the interior of the unit. Since this door mechanism defines a portion of the air flow path it is preferably sealed to prevent water leakage between the exterior of the unit into the indoor air flow stream and to prevent air leakage between the indoor flow path and the exterior of the unit. Additionally, this door arrangement must be sufficiently strong that integrity is maintained while the unit is shipped and being erected in place. Often, rooftop units are raised in position utilizing an overhead crane creating significant structural stress on the unit. The door latch mechanism must maintain the door in position notwithstanding this construction stress.
Previous door securing arrangements included engaging metal to metal contact surfaces. These arrangements had the problem of allowing no tolerance such that the severe strains during erection might cause separation of components beyond the tolerance of the latch resulting in incomplete door sealing. Metal to metal components further had the problems of difficult sealing and hard to operate mechanisms and presented difficulties for the serviceman.
The herein disclosed latch mechanism utilizes rolling contact surfaces to engage inclined contact angles to secure the door in position. Sufficient overlap is provided between the roller contact and the contact angle to allow relative displacement between the two and still provide for complete sealing of the unit. Additionally, by providing rolling contact surfaces an assembly is utilized wherein the entire door mechanism operates smoothly and freely and wherein access to the unit is both dependable and not a problem for the serviceman.